Flora of North America species comparison

Variety glabrata apparently is morphologically discontinuous from var. squarrosa where their ranges closely approach each other (but do not meet) in Texas, and they might be treated as separate species, especially in view of the treatment here of Liatris compacta at specific rank. Within var. squarrosa as treated here, plants along the Gulf coast tend to have much reduced phyllary vestiture (var. alabamensis) and perhaps represent the precursor to var. glabrata. Involucres of var. squarrosa sometimes approach the morphology of L. hirsuta; this appears to be parallel expression of ancestral similarity, because such plants often are long-separated from the geographic range of L. hirsuta. Heads tend to be more numerous and more crowded in var. glabrata than in var. squarrosa.

(Discussion copyrighted by Flora of North America; reprinted with permission.)